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Effects
of Glucosinolate-Rich Broccoli Sprouts on Urinary Levels of Aflatoxin-DNA
Adducts and Phenanthrene Tetraols in a Randomized Clinical Trial in He Zuo
Township, Qidong, People's Republic of China.
Cancer Epidemiol Biomarkers Prev. 2005 Nov;14(11):2605-13.
Kensler TW, Chen JG, Egner PA, Fahey JW, Jacobson LP, Stephenson KK, Ye L, Coady
JL, Wang JB, Wu Y, Sun Y, Zhang QN, Zhang BC, Zhu YR, Qian GS, Carmella SG,
Hecht SS, Benning L, Gange SJ, Groopman JD, Talalay P.
Department of Environmental Health Sciences, Bloomberg School of Public Health,
Johns Hopkins University, Room E7541, 615 North Wolfe Street, Baltimore, MD
21205. tkensler@jhsph.edu.
Residents of Qidong, People's Republic of China, are at high risk for
development of hepatocellular carcinoma, in part due to consumption of
aflatoxin-contaminated foods, and are exposed to high levels of phenanthrene, a
sentinel of hydrocarbon air toxics. Cruciferous vegetables, such as broccoli,
contain anticarcinogens. Glucoraphanin, the principal glucosinolate in
broccoli sprouts, can be hydrolyzed by gut microflora to sulforaphane, a potent
inducer of carcinogen detoxication enzymes. In a randomized, placebo-controlled
chemoprevention trial, we tested whether drinking hot water infusions of
3-day-old broccoli sprouts, containing defined concentrations of glucosinolates,
could alter the disposition of aflatoxin and phenanthrene. Two hundred healthy
adults drank infusions containing either 400 or <3 mumol glucoraphanin nightly
for 2 weeks. Adherence to the study protocol was outstanding; no problems with
safety or tolerance were noted. Urinary levels of aflatoxin-N(7)-guanine were
not different between the two intervention arms (P = 0.68). However, measurement
of urinary levels of dithiocarbamates (sulforaphane metabolites) indicated
striking interindividual differences in bioavailability. An inverse association
was observed for excretion of dithiocarbamates and aflatoxin-DNA adducts (P =
0.002; R = 0.31) in individuals receiving broccoli sprout glucosinolates.
Moreover, trans, anti-phenanthrene tetraol, a metabolite of the combustion
product phenanthrene, was detected in urine of all participants and showed a
robust inverse association with dithiocarbamate levels (P = 0.0001; R = 0.39),
although again no overall difference between intervention arms was observed (P =
0.29). Understanding factors influencing glucosinolate hydrolysis and
bioavailability will be required for optimal use of broccoli sprouts in human
interventions.
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